1. Field
The embodiments of the present invention relate to an organic light-emitting display apparatus and a photo mask for manufacturing the same.
2. Description of the Related Art
An organic light-emitting display apparatus includes two electrodes and an organic emission layer therebetween. Electrons from one electrode and holes from the other electrode are combined in the organic emission layer to form excitons, which emits light as they drop to a lower energy level.
Such an organic light-emitting display apparatus includes a plurality of pixels. Each pixel includes an organic light-emitting diode (OLED) that is a self-lighting device, a plurality of thin film transistors (TFTs) that include a switching TFT and a driving TFT, and a capacitor that is used for driving the OLED.
It is desired for the gate voltages of the driving TFT to have a wide driving range so as to allow adequate regulation of the amplitude of gate voltages Vgs of the driving TFTs to enable abundant gradations of displayed color intensity. To this end, a design to increase (e.g., maximize) a channel length of a driving semiconductor layer is desired. When a driving TFT is designed such that the driving semiconductor layer has a long channel length in a limited space, it is difficult for the driving semiconductor layer to have a constant channel width. When the channel width of the driving semiconductor layer is not constant, limitation problem may arise in that the effective channel length may be shorter than a predicted length (e.g., an expected length) due to carriers that move along the shortest distance.